KR20100029316A - Current control apparatus for led illumination - Google Patents

Abstract

PURPOSE: A constant current control device of an LED is provided to reduce the volume of a power supply and prevent the breakdown of the LED by comprising the minimum circuit. CONSTITUTION: A power supply unit is comprised of a condenser and a high pass filter including a resistor which is connected in parallel to the condenser. The power supply unit restricts the maximum current by controlling the cutoff band of a cutoff frequency by controlling a filter constant of the cutoff frequency. A rectifier is comprised of a bridge diode. A current controller is comprised of a resistor connected to a positive power node of the rectifier, a diode connected to a negative node, and a transistor connected between the resistor and the diode. The current controller controls the current including a pulsating current. A protector protects the devices of the current controller by cutting off the circulating current.

Description

Constant current control device for LEDs for lighting {CURRENT CONTROL APPARATUS FOR LED ILLUMINATION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED constant current control device for illumination, and more particularly, to an illumination constant current control device including a constant current supply circuit for driving a load composed of a plurality of illumination LEDs.

LED lighting device is a light source to replace the existing lighting devices such as incandescent lamps and fluorescent lamps, has received a lot of attention due to its high efficiency and long lifespan, and its technical development is being actively conducted, and it uses modular lighting devices in actual use. The LED lighting module may be configured in series and in parallel, and may also variously configure the light source as a combination thereof. In any case, the LED lighting module cannot be used directly from AC 220V, which is a commonly used power source, or in some regions, but can be used safely only by supplying suitable power by converting the supplied power.

 Commonly used methods to supply proper power use a switching-mode power conversion supply known as SMPS, which uses a flyback method, a buck conversion method and a semi-bridge conversion method. It is available in single and plural forms. In addition, the converted low voltage DC power supply can supply a constant current to the LED lighting module using a pulse width modulated signal.

In general, LED modules are divided into signal and lighting. In the past, the main power supply method was a constant voltage method that supplies a constant voltage to both ends of the LED as a safe LED driving method. The power consumption of is increased, and as the temperature rises during driving, a phenomenon that occurs when driving at a constant voltage causes an abnormally large current to flow, which causes the LED to break down due to an interaction in which the current increases again. Current limiting is known as a safer method of driving LEDs.

The constant current power supply for driving the LED module for safe lighting can be achieved by using a commercially available integrated circuit type device. This limits the current using a PWM (pulse width modulation) form of the method, which is generally known and currently the most used.

However, the methods described above are divided into a part of converting a commercial power supply into a DC voltage of a low voltage and a part of processing a converted power supply to achieve current control, thus requiring various integrated circuits and additional circuits. In addition, there is a disadvantage that the size increases. This is the most worrying problem in the industry, the application of the power supply and the load LED is difficult to make a one-piece, the application is delayed, even when making a one-piece, when the design is bulky, there is a very disadvantageous side. In addition, there are many disadvantages such as increased defects and higher production costs due to complicated circuits.

Accordingly, an object of the present invention is to supply a constant current to a load consisting of LEDs for lighting, and is constant from an AC AC power source to a load without using a complicated method such as a separate power supply such as SMPS or a pulse width modulated power supply. It is to achieve a method of limiting the current flowing to the load as desired while supplying current.

In order to achieve the above object, the device according to the present invention includes a power supply unit having a current limiting function, a rectifying unit for converting AC into a direct current, a current control unit for limiting the amount of current supplied to a load-loaded LED, and a load; When the amount of current supplied to the large amount of current is instantaneously characterized in that it comprises a freewheeling function for maintaining the forward direction of the current and a protection device to prevent the reverse flow of the current.

Due to the device according to the present invention, the overcurrent supply problem, which is the biggest problem when driving the LED for lighting, can be reduced to a minimal circuit configuration, and the volume of the power supply device can be drastically reduced as well as the problem of abnormal destruction of the LED. In addition, it is possible to reduce the production cost by reducing the number of components. Therefore, the problem of increasing the size of the device due to the use of a separate power supply such as a conventional SMPS, high production cost, and the problem of difficult design due to the excessive volume when the power supply and load LEDs are integrated And so on.

1 shows a general block diagram of an apparatus according to the invention, and FIG. 9 shows an example of the actual circuit of each component of the block diagram. Hereinafter, specific configurations and operations will be described with reference to the accompanying drawings.

2 and 3 is an implementation circuit diagram of a power supply unit having a maximum current limit function, the actual configuration is configured in the form of a high-frequency pass filter, the maximum pass current in the commercial power supply by adjusting the cutoff band of the cutoff frequency by adjusting the filter constant Can be limited. The formula for calculating the cutoff frequency is as follows.

 Where Fc is the cutoff frequency. In the case of commercial power supply, 60 Hz is used in South Korea, and the high-frequency pass filter uses a maximum current at a frequency above the cutoff frequency. Therefore, when the cutoff frequency is set to 60 Hz or more, the cutoff frequency (Fc) is passed depending on which frequency is set. The amount of current can be limited and kept constant. For example, set the constant to lower the cutoff frequency when increasing the current supplied to the load. For example, increase the value of capacitor (C) and increase the value of resistor (R). Also, when lowering the current supplied to the load, set the constant to the higher cutoff frequency. For example, lower the capacitor's value (C) and lower the resistor's value (R). In the actual circuit, various modifications may be used as shown in FIGS. 2 and 3, and used in the form of a high pass filter.

Figure 4 shows the rectifying unit, a generally known half-wave rectifying method and full-wave rectifying method can be used, this embodiment shows that the full-wave rectifying method.

5 shows a basic configuration of the current regulator, and FIGS. 6 and 7 show a current regulator having a function of an arbitrary adjuster. The main operation of the current regulator serves to prevent the current including the pulse flow component passing through the rectifier from passing over a certain current. The current waveform before passing through the current controller is shown in FIG. 9 and the current waveform after passing is shown in FIG. 10. appear.

An example of a circuit actually configured will be described with reference to FIG. 5, in which power is passed through the rectifier, positive power is applied through node 9, and negative power is applied through node 10 to apply voltage to D5. In this case, the applied voltage is maintained at a limit voltage maintained at a constant voltage level by D5. The voltage held by D5 is supplied to the base terminal of Q5 again, and the current corresponding to the supplied voltage is supplied to the load through node 9-> Q5-> node 11. At this time, in order to limit the current flowing in Q5, the voltage applied to the base of Q5 should be determined in the linear driving section of Q5. As a method to determine this, the input versus output graph provided by the manufacturer of Q5 is used or experimentally. One way is to measure the current flowing by adjusting the input to the base of Q5. In addition, when the voltage is determined, it can be determined by selecting D5 as a device that can limit the voltage, such as a Zener diode. FIG. 6 illustrates a case in which the amount of current supplied to the load through Q4 is increased by Darlington connection of Q3 and Q4 as another application embodiment of the current controller. FIG. 5 is a circuit modified to limit and change. The maximum supply current flowing through Q6 can be adjusted by adjusting the position of the middle tap of VR1 while the voltage of D6 is adjusted so that the voltage supplied to the base of Q6 is changed by resistance distribution, and finally the amount of current flowing through Q6 can be adjusted. have.

In the case of D4, D5, and D6 used in the above example, the same result is obtained even if the device is a variable voltage such as a zener diode, a constant voltage regulator, and a fixed voltage is output. It is a well known fact. In the case of devices labeled Q4, Q5, and Q6, it is common that all devices that can limit the current passing through the input such as transistors, FETs (field effect transistors), and IGBTs can obtain the same result.

8 is a detailed circuit diagram illustrating a power supply unit, a rectifier unit, and a current controller according to the above description. Referring to the flow of current in FIG. 8, when commercial AC power is supplied through node 21 and node 22, positive power is applied to node 21 and negative power is applied to node 22. In this case, it has a frequency component of 60Hz 220V, so it passes only the preset amount of current due to the action of the high pass filter C1 and R1. The method for determining the amount of passing current follows the above method. The power passing through the power supply configured in the form of a high-frequency pass filter passes through the full-wave rectifier D1 and is converted into a direct current pulse wave form. The pulse wave form of direct current undergoes a smoothing process through C3 and is applied to the current controllers R4, D2, and Q1. The voltage applied to R4 and D2 is applied to terminal 2 of Q1, which is the base terminal of Q1, by the limited voltage at D2, and a current corresponding to the applied voltage is applied to C4 through Q1, and smoothing process at C4. The power is supplied to the load through node 23 and node 24 via the control. Negative power is applied to node 21 and positive power is applied to node 22 as described above.

11 shows a protection device of the present invention. D13 acts as a freewheeling diode when the supply current is momentarily interrupted. In other words, if the power is disconnected from node 35 and node 36, if the load contains inductance components, the current tends to flow continuously. In this case, it rotates from node 38-> D15-> D13-> D11-> node 37 load. It plays a role of flowing electric current. This protects Q8 in the current regulator. In addition, D11 and D15 are reverse flow prevention diodes which serve to make the current applied to the load always be in a constant direction. The protection unit may include or delete the entire circuit as necessary, for example, when a component included in a load does not have an inductor component or a large current does not flow.

12 is a view showing an embodiment of the present invention with the protection device added.

In other words, when the supply current is strong, the protection unit is added. The flow of current is explained when node 21 is supplied with positive power when node AC and node 22 are supplied. When negative power is applied, commercial AC power has a frequency component of 60Hz 220V in Korea, so it passes only the preset amount of current due to the action of C14 and R16, the high pass filter. The method for determining the amount of passing current follows the above method. The power passing through the power supply configured in the form of a high-frequency pass filter passes through the full-wave rectifier D12 and is converted into a direct current pulse wave form. The pulse wave form of DC goes through the smoothing process through C15 and is applied to the current controllers R15, D14, and Q8. The voltage applied to R15 and D14 is applied to terminal 2 of Q8, which is the base terminal of Q8 only by the limited voltage at D14, and a current corresponding to the applied voltage is applied to C16 through Q8 and the smoothing process is performed at C16. The power is applied to the protection device parts D11, D13, and D15. At this time, D13 provides a current path from D15-> D13-> D11 when the power supply is momentarily cut off at the front end to prevent the element of the front end from being destroyed.D13 does not work when power is normally supplied. D11 and D15 supply current only in the forward direction. The current passing through the protection device is supplied to the load through the nodes 23 and 24. Negative power is applied to node 21 and positive power is applied to node 22 as described above.

13 shows another embodiment of a power supply unit in an actually configured circuit device.

10 LEDs for lighting are connected in series to form a group, and 3 groups are connected in parallel to form a load part.The driving power is supplied with a constant voltage through a 30V zener diode applied in the current regulator circuit. Since one driving current of LED is about 20mA, the actual resistance of LED load part for lighting is less than about 350Ω. When we look at the filter of the AC input current limiter in the power supply, the value of R is not significant because it is a very large value with respect to the resistance of the load. Considering the current derived from the value of C, if the element value of the capacitor is 1 pF, If the value is 100%, if the capacitor value is 0.01pF, the amount of current passing through it is reduced by about 1/100 times.

According to the formula of the cut-off frequency described above, if 100% of the current passes through 60Hz or more, the calculated cut-off frequency calculated by the element value of the circuit constituting the actual load part has a value of about 6 to 8 Hz, so it is 1/10. The supply is limited to twice the current, and the result is that the current is lowered by passing through the two-stage high frequency filter, which can be obtained by easily combining the R and C values according to the load configuration of the lighting LED. have.

As described above, in order to supply a constant current to a load composed of a lighting LED according to the present invention, a constant power supply from the AC power supply to the load without using a complicated power supply such as a separate SMPS or a pulse width modulated power supply. While supplying current, the current flowing to the load can be limited to the value desired by the designer.

1 is a simplified diagram of a device using the present invention

2 is an implementation circuit diagram of a power supply unit;

3 is another embodiment of a power supply circuit

4 is a diode bridge rectification circuit diagram

5 is a circuit diagram of the current control unit

6 is another implementation circuit diagram of the current regulator;

7 is a circuit diagram of the current adjustment unit with the current arbitrary adjustment function added;

8 is an implementation circuit diagram of the present invention 1

9 shows the current waveform through the diode bridge

10 is a current waveform passing through the current control unit

11 is a circuit diagram of the protective device

12 is a circuit diagram 2 of the present invention.

FIG. 13 is a circuit diagram showing an actual power supply unit.

Claims (3)

In the constant current control device of the LED for lighting, It is connected to AC power and consists of a high pass filter including a capacitor and a resistor connected in parallel with the capacitor.

A power supply that can limit the maximum current by adjusting the cutoff band of the cutoff frequency by adjusting the filter constant of A rectifier connected to the power supply and configured as a bridge diode; Comprising a resistor connected to the positive power node of the rectifier, a diode connected to the negative node, a transistor connected in the middle of the resistor and the diode, so as not to pass a current including the pulse flow component passing through the rectifier to the predetermined current or more. And the current control unit, and It characterized in that it comprises a protective device consisting of a diode which serves to protect the elements of the current control unit by blocking the rotating current caused by the inductance component of the load when the current supplied to the current control unit is cut off Constant current control device for LED lighting. The constant current control device of claim 1, wherein the current control unit is capable of arbitrarily adjusting the amount of current by connecting the transistor to Darlington or by changing a voltage supplied to the transistor by a variable resistor. The constant current control of the lighting LED according to claim 1 or 2, wherein the power supply unit has a number of capacitors and resistors connected to the circuit according to the setting of the cutoff frequency so that the current is limited according to the load capacity. Device.

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